【作者】 雷宣扬；

【导师】 宋希庚；

【作者基本信息】 大连理工大学 ， 动力机械及工程， 2003， 硕士

【摘要】 曲轴是内燃机最为重要的部件，曲轴的模拟计算是一个非常有意义的研究领域。由于曲轴的几何形状、边界条件和作用载荷都非常复杂，要尽量精确地模拟曲轴的振动特性，选择合适的计算模型是其中关键环节之一。从以前研究的状况来看，空间实体有限元是最为合适的方法，但因为受到计算规模的限制，它目前只被应用于静力学分析或简单模态分析；其它一些建模方法因为过于简化或适用范围太窄，所计算的结果与实际相差较大。综合考虑计算规模与结果精度，结合曲轴的结构与运行特点，本文提出以考虑剪切变形与转动惯量的空间TImoshenko梁单元为基础为曲轴建立有限元模型。 本文首先叙述结构动力学中的有限元法原理；其次介绍Timoshenko梁的理论与特点，论述了剪切变形、转动惯量等因素对梁的振动特性的影响，揭示了Timoshenko梁与Euler梁或杆件的本质区别；在此基础上，详细地陈述了对曲轴系统整体结构建立有限元模型的方法与过程；应用此方法，以一单缸发动机的曲轴及一四缸发动机曲轴为实例，采用ANSYS软件对它们的振动特性进行分析。最后，为使本文的方法得以推广与应用，采用VC++6.0结合ANSYS与MatLAB编制了一个及模拟、计算和分析于一体的应用软件系统。 以单缸发动机曲轴为模拟对象，分别采用实体有限元与本文方法进行模态分析，通过比较发现两者的结果在数值上非常接近，形态上完全一致。同样采用本文的方法分析一四缸发动机曲轴，并与其它研究的结果与实验数据进行对比，其结果表明，本文方法模拟的结果更为接近实验数据。紧跟其后，本文对此四缸发动机曲轴进行了谐响应分析与动力学时程分析，分析的结果前后互相吻合。 通过多个方面比较后表明：本文所提出的方法在结果精度上与实体有限元法相差不大，与实验结果非常接近；计算规模上远远小于实体有限元法。总之，本文提出的方法建模过程简洁、直观，非常适用于曲轴的动态振动特性分析。更多还原

【Abstract】 Crankshaft is the most important part of the I.C.E. Numerical simulation in crankshaft is a very significative research field. Since the shape, the boundary condition and the load of the crankshaft being very complex, to simulate the vibration behavior of crankshaft well, a good computational method is very important. According to the foregone research experience, the solid FEM can be the best method for solving this problem. But because of the limit of computational scale, it is just applied in the analysis of statics and mode. Since the other methods being too simple or the application fields being very narrow, the results of computation are much different from experimental data. Considering the computational scale and the precision of the computational results, together with the structure and working style of crankshaft, the spatial Timoshenko beam element count of shear deformation and inertia moment is suggested to be applied for modeling crankshaft in this thesis.Firstly the principle of FEM in structure dynamics is presented. Then the theory of Timoshenko beams is introduced and the difference between Timoshenko beams and Euler beams is explained. Then the method and process of building FEM for the crankshaft is described in detail. Further more, using the method and ANSYS software, the Vibration behavior of the crankshaft in an one-cylinder engine and a four-cylinder engine are analyzed. At last, based on VC++ 6.0 and MatLAB, a software that can simulate, compute and analysis the dynamic behavior of any crankshaft is compiled.By using the solid FEM and the method decided in this thesis respectively, the vibration mode of crankshaft hi the one-cylinder engine is simulated. Results of two methods are very similar. The vibration mode of the crankshaft in the four-cylinder engine is analyzed by the presented method too, and the calculation results are compared with that results and the experimental data in other publications. It indicates that the results obtained by the method in this thesis are more effective than those presented in other publications and in good agreement with the observed data. In addition, the harmonic response and the dynamic response in time domain of crankshaft in the frontal four-cylinder engine are simulated.According to the contrast in several aspects, it is proved that the method suggested in this thesis is comparative with solid FEM for simulating the dynamic behavior of crankshaft, and the computational results are in good agreement with the experimentation data. In particular, the quality of computation is far smaller than the latter. In a word, the method presented in this thesis is concision and straightforward, it is competent for simulating the dynamic behavior of crankshaft by my own view.更多还原